Closed-loop multi-stage chilled filter system

ABSTRACT

A series of vertically oriented filters of decreasing pore size is sealed from the atmosphere. Pressurized gas is used to force the liquid to be filtered through the filters. The filter stages are thermally insulated from ambient temperatures in order to maintain the liquid passing through at a reduced temperature. Each filter stage has a removable lid, which provides convenient access for replacing the filter cartridge, allowing it to be changed without disturbing the thermally insulated sidewalls of the filter stage.

TECHNICAL FIELD

This application relates to filtering. More specifically, it relates toa multi-stage, chilled filter arranged in a closed-loop configuration.

BACKGROUND

Filtering is a necessary step in the process of essential elementextraction. Traditionally, the vertically oriented in-line and T-formfilter housings that exist require the main body of the housing to belifted off the base in order to replace the filter cartridge inside.

In legal, adult-use markets, sales of cannabis extracts are growing tentimes faster compared to the sales of dried cannabis, and extractsaccount for over 60% of revenue. With legalization, consumer preferencesare shifting from dried cannabis to extracted cannabis products.However, the scent and flavors of cannabis can be undesirable in manyinfused products because of excess lipids, plant matter and impuritiespresent in currently available extracts.

U.S. Pat. No. 9,155,767 to Hospodor et al. relates to the extraction ofmedicinal cannabis compounds into an eluate, by separating a portion ofmedicinal cannabis compounds contained within a portion of eluate at afirst extraction target level, to provide enough clean solvent tocontinue extraction operations. A high efficiency concentrator processeseluate from one or more tanks, creating clean solvent when extractiontargets are met or when clean solvent is exhausted. This manages eluateconcentration levels and limits the quantity of concentrated medicinalcannabis compounds on site at any moment in time.

U.S. Pat. No. 9,655,937 to Jones discloses extraction devices, methods,and systems. Example devices have a solvent chamber, a plant materialchamber, a collection chamber, and a solvent return that create asealed, closed-cycle extraction and/or solvent purification process. Anyextractable plant material can be used in the disclosed devices,methods, and systems although in some examples some form of the cannabisplant is used.

This background information is provided to reveal information believedby the applicant to be of possible relevance to the present invention.No admission is necessarily intended, nor should be construed, that anyof the preceding information constitutes prior art against the presentinvention.

SUMMARY OF INVENTION

The present invention is directed to a system of chilled filtersconnected in a closed-loop configuration for use in the extraction ofessential elements from plant material. When extracting essentialelements, the plant material is washed and/or soaked in a solvent suchas ethanol to result in a crude oil and ethanol mixture, for example.The system of chilled filters is used to filter the crude oil andsolvent mixture to remove particulate matter, and may be used atdifferent stages of the extraction process. In particular, the filtersystem may be used as part of a process for extracting cannabinoids fromcannabis plants, for example for medicinal purposes.

Disclosed herein is a filtration system comprising a solvent vessel, aplurality of filter stages and the same plurality of transfer tubes.Each filter stage has a thermally insulated cylindrical side wall; a lidthat is removable from said wall; a replaceable, elongated filtercartridge; a support configured to locate a base of said filtercartridge centrally in the filter stage; an inlet port in the lidlocated to introduce liquid into the filter cartridge; an inlet portconfigured for introducing pressurized gas outside of the filtercartridge; and a base with an outlet port that drains fluid from outsidethe filter cartridge. The solvent vessel has a thermally insulated sidewall; an inlet port configured for introducing pressurized gas; and anoutlet tube having a first end located at a bottom region of the solventvessel and a second end located outside the solvent vessel. The transfertubes are each removably connected at an outlet end thereof to one ofthe inlet ports in one of the lids of the filter stages; and at an inletend thereof to either the second end of the outlet tube of the solventvessel or the outlet port of another of said filter stages such that thesolvent vessel and the filter stages are connected in series.

BRIEF DESCRIPTION OF DRAWINGS

The following drawings illustrate embodiments of the invention, whichshould not be construed as restricting the scope of the invention in anyway.

FIG. 1 is a schematic diagram of the closed-loop, multi-stage, chilledfilter system, according to an embodiment of the present invention.

FIG. 2 is a flowchart of a process undertaken using the system of FIG.1.

FIG. 3 is a schematic diagram of an alternate embodiment of theclosed-loop, multi-stage, chilled filter system of the presentinvention.

DESCRIPTION A. Glossary

Cannabinoids are a group of chemicals that act on cannabinoid receptorsin the body, numerous of which are found in the cannabis plant.Cannabidiol (CBD) is one of the active cannabinoids found in cannabisand is used for medicinal purposes. Tetrahydrocannabinol (THC) is apsychotropic cannabinoid and is the main psychoactive ingredient ofcannabis. THC also has medicinal uses. THCa is the non-psychoactive formof THC.

Crude oil is a term for the description of condensed, non-filtered oil,i.e. oil that is non-winterized and not treated via charcoal, clay andsilica. The crude oil contains the essential elements. Winterizationrefers to the removal of unwanted plant waxes and lipids.

B. Apparatus

Referring to FIG. 1, a closed-loop, multi-stage filter system 10 isshown, which includes a solvent vessel 12, a first filter stage 14, asecond filter stage 16 and a third filter stage 18 all connected inseries, and a collection vessel 19 for collecting filtered liquids fromthe system.

The solvent vessel 12 contains the crude oil and solvent mixture 20 thatis to be filtered. The crude oil and solvent mixture 20 is the liquidthat is drawn out of an extractor column, for example, i.e. after theplant material in the extractor column has been washed and/or soakedwith the solvent. The crude oil contains essential elements and isdissolved in the solvent. The mixture also contains some unwantedresidual plant matter and other undesirable components. Before the crudeoil and solvent mixture 20 is placed in the solvent vessel 12, it mayundergo one or more pre-filtering steps. For example, the crude oil andsolvent mixture 20 may be pre-filtered with activated charcoal, clayand/or silica. The charcoal removes pigments, chlorophyll, heavy metalsand particulates. The clay primarily removes pigments. The silicaremoves very fine plant matter and other particulates.

The stainless steel solvent vessel 12 has an outer wall 22, an innerwall 23 and a base 24. The outer wall 22 and inner wall 23 form a sidewall or jacket that is filled with chilled, pressurized liquid CO₂ inorder to keep the contents of the solvent vessel 12 cool. Thermalinsulation 26 is wrapped around the outer wall 22 of the filter stage12. In other embodiments, the jacket could be evacuated to providethermal insulation, and the thermal insulation is not necessary. Themain requirement is that the inner wall 23 of the solvent vessel bethermally insulated from ambient temperatures of the surroundingatmosphere in order to keep the contents of the vessel cool. Optionally,the jacket includes the base 24 of the solvent vessel 12, and the basemay be further thermally insulated.

A removable lid 28 seals to the top of the solvent vessel 12 so that thecontents of the vessel can be pressurized via inlet port 30. Nitrogengas under pressure is fed into the vessel 12 via inlet tube 32 and valve34. As the solvent vessel 12 is pressurized, the crude oil and solventmixture 20 within it is forced out of the vessel through exit tube 38,which forms an airtight seal around its outside with the lid 28. Theexit tube has an inlet in the bottom region 39 of the solvent vessel 12so that liquid in the solvent vessel can readily enter it.

The exit tube 38 is connected via an airtight connector 40 outside ofthe solvent vessel 12 to a transfer tube 42. The transfer tube 42 isconnected in turn via an airtight connector 44 and 3-way valve 45 to theinlet port 46 of the first filtering stage 14. Optionally, the transfertube 42 is thermally insulated. Additional solvent may be introduced viathe inlet tube 47 connected to the 3-way valve 45.

The first filter stage 14 has an outer side wall 50 surrounded by athermal insulator 51, an inner side wall 52 spaced apart from the outerside wall, a lid 54 that seals to the top of the filter stage and a base56. The outer wall 50 and inner wall 52 form a side wall or jacket thatis filled with chilled, pressurized liquid CO₂ in order to keep thecontents of the filter stage 14 cool. While different configurations ofthermal insulation are possible, the main requirement is that the innerwall 52 of the filter stage 14 is thermally insulated from ambienttemperatures in order to keep the contents of the stage cool.Optionally, the jacket includes the base 56 of the filter stage 14, andthe base may be further thermally insulated. The first stage 14 issealed against the atmosphere so that it can be pressurized. The firststage 14 is mounted on supports 58.

A support 60, which is positioned in the bottom of the filter stage 14,has a locating feature such as a beveled edge 62. The locating feature62 serves to position the lower portion or base 61 of a replaceablecylindrical filter cartridge 64 centrally in the filter stage 14. Inother embodiments, different shapes of the support are possible. In thisembodiment, the filter cartridge is a polypropylene filter with a poresize in the range of 10-15 μm. Other filter sizes may be used in otherembodiments. At the top of the filter stage 14 there is a guide ring 66,which serves to direct the filter cartridge 64 along the axis of thefilter stage and maintain an upper portion 63 of the filter cartridgealigned axially within the filter stage. In other embodiments the shapeof the guide ring 66 is different.

The support 60 has through holes 65 to permit the passage of filteredliquid from a volume 67 of the filter stage above the support to avolume 69 below it, which is adjacent to and in fluid communication withthe outlet port 70. The guide 66 has through holes 71 to permit thepassage of filtered liquid from a volume 73 above the guide to thevolume 67 below the guide. Supports 60 and guides 66 may have slots orgaps with other shapes to provide fluid communication between thevolumes 73, 67, 69 of the solvent vessel. The top of the filtercartridge 64 is sealed to the underside of the lid 54 with an O-ring 68.

The crude oil and solvent mixture 20 enters the filter stage 14 throughinlet port 46, which directs the mixture into the inner region 75 of thefilter cartridge 64. The mixture is then filtered as it passes outthrough the side walls and base of the filter cartridge 64. The filteredmixture collects in the bottom of the filter stage 14 and passes out ofit through exit port 70 in the base 56 of the filter stage.

When required, the cartridge 64 is replaced by disconnecting transfertube 42 from the lid 54, removing the lid from the filter stage 14,lifting out the cartridge, and then placing a new cartridge in itsplace. By removing only the lid 54 from the filter stage 14, the sidewalls 50, 52 can remain in place, together with the thermal insulation51. This makes it convenient to change the filter cartridge 64,particularly if the filter stage is large. In some embodiments, the sidewalls 50 can be 1 m tall or more. As well as making the filter cartridgemore convenient to change, taller filtration stages can be used withinthe same headroom compared to stages that require the outer walls to belifted to change the filter cartridge.

A connector 78 connects a second transfer tube 79 to the outlet port 70of the filter stage 14. A second port 80 in the lid 54 of the filterstage 14 allows for nitrogen to be supplied directly to the filter stagethrough tube 82 and valve 84. This is useful in case a blockage occursupstream in the system 10.

The transfer tube 74 is connected via an airtight connector to the inletport of the second filtering stage 16. The second filter stage 16 issimilar to the first filtering stage 14, except that the filtercartridge 90 has a smaller pore size, which in this embodiment is in therange 3-10 μm. Other filter sizes may be used in other embodiments.

The outlet port at the bottom of the second filter stage 16 is connectedvia a third transfer tube to an inlet port in the top of the lid of thethird filtering stage 18. The third filter stage 18 is similar to thefirst and second filter stages 14, 16, except that the filter cartridge92 has an even smaller pore size, which in this embodiment is 1 μm.Other filter sizes may be used in the third filter stage 18 in otherembodiments, including filter sizes that are smaller than 1 μm.

The outlet port at the bottom of the third filter stage 18 is connectedvia a connector and collection pipe 94 to the collection vessel 19, inwhich the filtered crude oil and solvent mixture 96 is collected. Thecollection vessel 19 is covered or sealed from the atmosphere with apressure relief valve 98, although, optionally, it may be uncovered.

A benefit of having the solvent vessel 12 and the three filter stages14, 16, 18 sealed from the atmosphere is that it reduces the amount ofcondensation of water into the chilled solvent. This would otherwisedilute the solvent and reduce its effectiveness.

C. Exemplary Process

In use, the crude oil and solvent mixture is chilled either beforeplacing it in the solvent vessel 12 or while it is in the solventvessel. After this, nitrogen is fed into the solvent vessel 12 at apressure in the range of about 70-210 kPa (10-30 psi). When the filtersystem 10 is used for the extraction of essential elements from cannabisand the solvent used is ethanol, the crude oil and solvent mixture ismaintained at a temperature between −40° C. and −20° C. in the solventvessel 12, and remains below −10° C. as it passes through the threefilter stages 14, 16, 18.

Referring to FIG. 2, the first step of the process is to chill the crudeoil and ethanol mixture in step 200 to a temperature between −40° C. and−20° C. In step 204, the crude oil and ethanol mixture is filteredthrough a 10-15 μm filter in the first filtering stage 14. In step 208,the crude oil and ethanol mixture is then filtered through a 3-10 μmfilter in the second filtering stage 16. In step 212, the crude oil andethanol mixture is finally filtered through a ≤1 μm filter in the thirdfiltering stage 18.

D. Variations

While the best presently contemplated mode of carrying out the subjectmatter disclosed and claimed herein has been described, other modes arealso possible.

The outlet tube 38 of the solvent vessel 12 may lead downwards from thebase 24 of the solvent vessel, in the same way that the outlet ports 70are located on the filter stages 14, 16, 18.

Referring to FIG. 3, an alternate filter stage 300 is shown. Multiplesuch filter stages can be connected in series as above. The filter stage300 includes a removable base 302 with jacketed sidewall 304 andsurrounding insulation 306, mounted on legs 308 or other equivalent rackor support. An inlet pipe 310 from the previous stage or from thesolvent vessel feeds fluid to be filtered into the stage, via theconnector 312 and inlet port 314. The fluid to be filtered is fed intothe volume 320 to the outside of the filter cartridge 325. As the fluidis filtered, it passes through the cartridge 325 to the volume 330 onthe inside of the cartridge, and then leaves the filter stage via outletport 340 in the removable base 302. Outlet pipe 342 transfers thefiltered fluid to the next stage or to the collection vessel 19. Thecartridge 325 is aligned with a guide 344 on the removable base 302 andwith a spacer 346 at the upper end of the cartridge. A further inletport 350 is used to introduce nitrogen gas if needed and/or solvent.Other valve and/or inlets may be included in the filter stage 300, e.g.for evacuating the jacket, filling it with chilled liquid CO₂, removingfluids from the stage and/or for introducing fluids into the stage.

The legs 308 or other equivalent support holds the body or main sidewall304 of the filter stage 300 off the floor by a distance that issufficient to detach the inlet and outlet pipes 310, 342 from theremovable base 302, lower the base and remove/replace the cartridge 325without having to move the sidewall 304 H1. This is possible whendistance H1 is greater than distance H2. Distance H1 is the height ofthe legs off the floor 360 and distance H2 is the height of thecartridge 325 plus the height of the removable base 302 with itspermanent fixtures (i.e. inlet port 314 and outlet port 340). It isimportant not to have to disturb the jacketed sidewall 304 so that theinsulation 306 does not need to be moved.

In some embodiments, the apparatus is portable so that it can be takento the different sites of various plant growers, to be used on anas-needed basis.

Different filter media may be used in this apparatus, such as clay,charcoal and silica.

In other embodiments within the purview of the present invention, otherplant materials besides cannabis may be processed. For example, lavenderand hemp may be processed, as well as other plants that producephytochemicals of interest, which include cannabinoids, terpenes, andflavonoids.

Temperatures that have been given to the nearest degree include alltemperatures within a range of ±0.5° C. of the given value.

In general, unless otherwise indicated, singular elements may be in theplural and vice versa with no loss of generality.

Throughout the description, specific details have been set forth inorder to provide a more thorough understanding of the invention.However, the invention may be practiced without these particulars. Inother instances, well known elements have not been shown or described indetail and repetitions of steps and features have been omitted to avoidunnecessarily obscuring the invention. For example, various ports,valves, tubes and other thermal insulation are not shown for clarity.Accordingly, the specification and drawings are to be regarded in anillustrative, rather than a restrictive, sense.

It will be clear to one having skill in the art that further variationsto the specific details disclosed herein can be made, resulting in otherembodiments that are within the scope of the invention disclosed. Allparameters, dimensions, proportions, relative proportions, materials,and configurations described herein are examples only and may be changeddepending on the specific embodiment. Accordingly, the scope of theinvention is to be construed in accordance with the substance defined bythe following claims.

The invention claimed is:
 1. A filtration system comprising a solventvessel, a plurality of filter stages and the same plurality of transfertubes wherein: each filter stage has: a thermally insulated cylindricalside wall; a lid that is removable from said wall; a replaceable,elongated filter cartridge; a support having a beveled edge thatpositions a base of said filter cartridge centrally in the filter stage;an inlet port in the lid located to introduce liquid into the filtercartridge; an inlet port located to introduce pressurized gas into thefilter stage outside of the filter cartridge; and a base with an outletport that drains fluid from outside the filter cartridge; the solventvessel has: a thermally insulated side wall; an inlet port forintroducing pressurized gas; and an outlet tube having a first endlocated at a bottom region of the solvent vessel and a second endlocated outside the solvent vessel; and the transfer tubes are eachremovably connected: at an outlet end thereof to one of the inlet portsin one of the lids of the filter stages; and at an inlet end thereof toeither the second end of the outlet tube of the solvent vessel or theoutlet port of another of said filter stages such that the solventvessel and the filter stages are connected in series.
 2. The filtrationsystem of claim 1 further comprising a guide positioned to locate anupper portion of the filter cartridge centrally in the filter stage. 3.The filtration system of claim 1 further comprising a seal between eachfilter cartridge and the lid of the corresponding filter stage.
 4. Thefiltration system of claim 1, wherein each support defines a fluidcommunication path from a volume above the support to a volume adjacentthe outlet port.
 5. The filtration system of claim 1, wherein each guidedefines a fluid communication path from a volume above the guide to avolume below the guide.
 6. The filtration system of claim 1, whereinthere are three filter stages and: a first of the filter stages isconnected to the solvent vessel and its filter cartridge has a pore sizeof 10-15 μm; a second of the filter stages is connected to the firstfilter stage and its filter cartridge has a pore size of 3-10 μm; andthe third of the filter stages is connected to the second filter stageand its filter cartridge has a pore size of ≤1 μm.
 7. The filtrationsystem of claim 1, wherein each filter cartridge is made frompolypropylene.
 8. The filtration system of claim 1, wherein the solventvessel has chilled liquid carbon dioxide in its side wall.
 9. Thefiltration system of claim 8, wherein the side wall of the solventvessel is at a temperature between −20° C. and −40° C.
 10. Thefiltration system of claim 1, wherein each filter stage has chilledliquid carbon dioxide in its side wall.
 11. The filtration system ofclaim 10, wherein the side walls of the filter stages are at atemperature of ≤−10° C.
 12. The filtration system of claim 1, whereinthe pressurized gas is nitrogen that is pressurized to 70-210 kPa. 13.The filtration system of claim 1, wherein the filtration system issealed from an external atmosphere everywhere except at the outlet portof the filter stage that is at an end of the series.
 14. The filtrationsystem of claim 13, wherein the outlet port of the filter stage that isat an end of the series discharges into a collection vessel.
 15. Thefiltration system of claim 14, wherein the outlet port of the filterstage that is at the end of the series discharges via a collection tubeinto the collection vessel.
 16. The filtration system of claim 1,wherein: the outlet port of the filter stage that is at the end of theseries discharges via a collection tube into a collection vessel; andthe collection vessel is sealed from an external atmosphere via apressure relief valve.
 17. The filtration system of claim 1, wherein thetransfer tubes are thermally insulated.
 18. The filtration system ofclaim 1, wherein the bases of the filter stages and a base of thesolvent vessel are thermally insulated from an external atmosphere. 19.The filtration system of claim 1, wherein the side walls of one or bothof the filter stages and the solvent vessel are evacuated.
 20. Thefiltration system of claim 1, wherein the bases of the filter stages anda base of the solvent vessel are double walled and are either evacuatedor filled with liquid carbon dioxide.
 21. The filtration system of claim1, wherein each filter stage comprises a further inlet located tointroduce solvent into the filter cartridge.